Noninvasive intra-partum, or electronic fetal monitoring (EFM), is a generally accepted standard of care in obstetrics. EFM provides a visual continuous beat-to-beat recording of the fetal heart rate and a recording of uterine activity. EFM shows how the fetus responds before, during, and after each contraction and provides a graphic record for review. The goal of electronic fetal monitoring is to assist in identifying possible problems of the fetus in order to reduce or relieve that distress. The device used for EFM is a cardiotocograph, and it usually consists of two sensors placed on the mother's abdomen and held in place with a strap or belt. One sensor, the tocodynamometer (TOCO) sensor, is a pressure-sensitive contraction transducer, and measures the intensity and duration of uterine contractions during labor. The other sensor measures fetal heart rate using Doppler ultrasound to detect motion of the fetal heart valves. An example of a monitor that utilizes these sensors is the Avalon fm20 manufactured by Philips (Philips Medical, Andover Mass.).
Fetal heart rate can be measured using a Doppler ultrasound probe placed on the mother's abdomen. Alternatively, the fetal heart rate can be measured using the fetal ECG using an electrode needle attached to the fetal scalp. The Doppler ultrasound method is more common and is less invasive. Fetal heart rate (FHR) Doppler ultrasound probes measure the change in frequency of ultrasonic waves as they reflect off of moving tissues within the body. Ultrasonic waves are transmitted by piezoelectric generators in the FHR probe and the reflected waves are detected by transducers in the same probe. According to the Doppler Effect, the frequency of the reflected waves is shifted higher or lower (depending on the direction of the movement) when the waves reflect off of a moving object within the body. The shift in reflected wave frequency creates a signal that is proportional to the movement and the beat-to-beat changes in this frequency signal are analyzed to calculate the fetal heart rate. Since this method uses ultrasound, the probe must be directly coupled such that there is no air between the probe and the skin. A coupling gel is used between the probe and the skin to allow the ultrasonic energy to pass from the probe to the skin. The FHR is plotted over time and clinicians are trained to interpret the FHR for any stresses placed on the unborn infant.
Clinicians commonly train for obstetrical procedures, such as EFM, using simulation. EFM is a key part of clinicians' training. In most training systems, the electronic fetal monitoring is simulated using a computer screen that is programmed to look like an EFM plot, rather than using an actual EFM monitor. Thus, clinicians are not able to practice using the EFM monitors that they will use on patients. Clinicians are not able to practice placement of the sensors, or any use of the actual device.
Consequently, there is a long felt need for a technology that could more accurately simulate the clinical experience of using EFM. For example, if the EFM signals could be physically simulated so that simulated uterine activity and fetal heart rate data could be presented on actual EFM devices, the realism of the simulation-based training would be improved and the clinicians in training would be able to learn to better interact with actual clinical monitors and devices during simulated crisis situations.